Disc gripping device

ABSTRACT

A disc gripping device is configured for gripping a disc by inserting at least three gripping members into a center hole of a disc and expanding at least one of the gripping members in a radial direction to push an inner circumferential face of the center hole. The at least three gripping members include a first gripping member having a disc contacting face for contacting the inner circumferential face of the center hole, a length of the disc contacting face being greater than a thickness of the inner circumferential face of the center hole; a second gripping member having a disc contacting face for contacting the inner circumferential face of the center hole, a length of the disc contacting face being equal to or smaller than the thickness of the inner circumferential face of the center hole, and a third gripping member having a disc contacting face for contacting the inner circumferential face of the center hole.

BACKGROUND

1. Technical Field

The present invention relates to a disc gripping device suitable to be used for gripping discs one by one which are loaded in a stacker of a device such as a disc dubbing device and a CD/DVD publisher.

2. Related Art

In a disc processing device such as a disc dubbing device, which writes data in multiple discs such as blank CDs, and a CD/DVD publisher, which can publish a disc using a produced disc by writing data and printing a label, generally, multiple blank discs or recorded discs are loaded into a stacker so that the discs are stacked in a thickness direction. Gripping devices for gripping a disc loaded in a stacker are known in JP-A-2003-257084 (Patent Document 1) and U.S. Pat. No. 6,802,070 (Patent Document 2).

In Patent Document 1, an optical disc clamping device is disclosed. In the optical disc clamping device, steel balls separated by equal angular distances in the same circle are pushed outward in a radial direction by an elastic force. The steel balls are inserted into a center hole from a front side of the disc to be pushed out to a rear side of the disc. When the steel balls are pushed to the rear side of the disc off the inner circumference face of the center hole, the steel balls are expanded outward in the radial direction depending on an elastic force, and the disc is gripped by the steel balls.

In Patent Document 2, a CD transporting device is disclosed. In this CD transporting device, a CD separation protrusion is formed on a gripping part of a gripping member for assuredly gripping one CD that is disposed in the uppermost position among CDs stacked in a thickness direction. In this CD transporting device, only the uppermost CD is gripped and lifted by pushing the three gripping parts inserted into the center hole of the CD and inserting the protrusions thereof into a gap between the CD and a CD stacked in the lower side.

In the optical disc clamping device disclosed in Patent Document 1, the steel balls pushed by an elastic force are forcedly inserted into the center hole of the disc to be lifted to the rear side of the disc. Accordingly, there is a possibility that an inner circumference face part or an edged end part of the center hole of the disc is damaged by the steel balls. In addition, in a case where discs are stacked up, when the steel balls are moved to a rear side of the uppermost disc, the steel balls contact the inner circumference face of the center hole of a lower disc. Thus, the steel balls cannot move inward in the radial direction when the upper and lower discs are tightly contacted to each other by an electrostatic force or the like, and there is a possibility that only the upper disc cannot be gripped.

In the CD transporting device disclosed in Patent Document 2, upper and lower discs are separated by the protrusion formed on the gripping part, and accordingly, only the upper disc can be gripped and lifted. However, the depth of a disc such as a CD differs by a disc manufacturer. In addition, there is a thickness difference between different types of discs such as between a CD and a DVD. Accordingly, a situation may arise where the position of the protrusion of the gripping part cannot be determined between the upper and lower discs, and only the upper disc cannot be gripped and lifted.

SUMMARY

An advantage of some aspects of the invention is to provide a disc gripping device capable of assuredly gripping and lifting a disc among stacked discs one by one.

In addition, another advantage of some aspects of the invention is to provide a disc gripping device capable of assuredly gripping and lifting a disc without causing any damage to the disc.

The advantages can be attained by at least one of the following aspects:

A first aspect of the invention provides a disc gripping device for gripping a disc by inserting at least three gripping members into a center hole of a disc and expanding at least one of the gripping members in a radial direction to engage an inner circumferential face of the center hole, wherein the at least three gripping members include: a first gripping member having a first disc contacting face for contacting the inner circumferential face of the center hole, a length of the first disc contacting face being greater than a thickness of the inner circumferential face of the center hole; a second gripping member having a second disc contacting face for contacting the inner circumferential of the center hole, a length of the second disc contacting face being equal to or smaller than the thickness of the inner circumferential face of the center hole, and a third gripping member having a third disc contacting face for contacting the inner circumferential face of the center hole.

When the gripping device according to an exemplary embodiment of the present invention is used, discs stacked in a thickness direction can be assuredly gripped and lifted one by one from the upper side. In other words, when the gripping members are inserted into the center hole of the uppermost disc among stacked discs and at least one gripping member is pushed in a radial direction, the disc contacting faces of the at least three gripping members are engaged with an inner circumferential face of the center hole of the disc.

At this time, the disc contacting faces of the gripping members pass through the center hole, and the uppermost disc is assuredly gripped by the three or more gripping members. For example, in a case where the number of the long gripping members are two or more, the long gripping members are disposed in the area of the inner circumferential faces which do not include the diameter of the center hole, and since the distance between the disc contacting faces of the long gripping members is smaller than the diameter of the center hole and the short gripping member does not protrude to the rear side of the upper disc, the lower disc is not lifted.

The first disc contacting face of the first gripping member may be preferably formed of an elastic member, and a part which is protruded to the rear side in the disc contacting face from the center hole goes into the rear side of the disc without being transformed elastically. In other words, the part goes into a gap between the rear side of the upper disc to be gripped and a front side of a lower disc. A disc contacting face of the short gripping member is pushed to only the inner circumferential face of the center hole of the uppermost disc. As described above, owing to the elastic transformation of the disc contacting face of the first gripping member, the disc is assuredly gripped, so that the disc also does not fall off the gripping members in the disc thickness direction. On the other hand, only a part of the disc contacting face of the first gripping member is in contact with the lower disc. Accordingly, when the gripping members are lifted, only the uppermost disc can be lifted assuredly.

In a case where the third gripping member is the long gripping member, the disc contacting face of the third gripping member may be preferably formed of an elastic member as well as the first gripping member.

In addition, in order to avoid damage to a disc when the disc is gripped, the disc contacting face of the second gripping member may preferably be formed of an elastic member.

Generally, the number of the gripping members is three. In this case, two of the three gripping members may be the long gripping members (first and third gripping members), and the remaining one may be the short gripping member (second gripping member).

When the gripping members are pushed in the radial direction, the position of an upper disc in the disc planar direction is fixed by the three gripping members, but a lower disc is pushed in the disc planar direction by the long gripping members. As a result, the lower disc slightly slides with respect to the upper disc. Although when the upper and lower discs are tightly contacted, the lower disc slides so as to permit air to enter between the upper and lower discs, and accordingly, the tight contact is alleviated or released. Accordingly, only the upper disc can be lifted assuredly.

In addition, since all of the first to third gripping members are configured to be able to move in a radial direction, a circumscribed circle of the gripping members can be reduced in size, and accordingly, it is easy to insert the gripping members into the center hole without touching the surface of the disc. Consequently, an insertion guide is not required.

In addition, the gripping member, of which the disc contacting face is formed of an elastic member, may have an elastic cylinder including a shaft member and an elastic member covering an outer circumferential face of the shaft member.

The disc gripping device according to an exemplary embodiment of the invention may be used for a disc processing apparatus having a disc storage for storing discs including a CD and a DVD wherein the discs are stacked in a thickness direction, for example, a CD dubbing apparatus or a CD publisher.

A disc gripping device according to an exemplary embodiment of the invention has a first gripping member which has a length of a disc contacting face contacting the inner circumferential face greater than a thickness of the inner circumferential face of the center hole, a second gripping member which has a length of a disc contacting face contacting the inner circumferential face equal to or smaller than the thickness of the inner circumferential face of the center hole, and a third gripping member having a disc contacting circumferential for contacting the inner circumferential of the center hole. With an appropriate number of the long and short gripping members, when the gripping members are inserted into an uppermost disc among stacked discs and are pushed in a radial direction, the uppermost disc can be gripped assuredly. In other words, when a length of the disc contacting face of the first gripping member is configured to be always greater than the thickness of a disc considering uneven thicknesses, only the uppermost disc can be always gripped and lifted regardless of uneven thicknesses of discs.

In a case where the disc contacting face of the first gripping member is also in contact with an inner circumferential face of the center hole of a lower disc, when the gripping member is pushed, the lower disc slightly slides by the first gripping member to alleviate or release the tight contact with the upper disc. Accordingly, only the upper disc can be assuredly gripped and lifted.

In a case where all the disc contacting faces of the first to third gripping members are formed of elastic members, there is an advantage that the disc is not damaged by the member members when the gripping members are pushed.

In another exemplary aspect of the invention, a disc gripping device for gripping a top disc from a stack of at least two discs includes a plurality of gripping members having respective disc contacting faces for contacting an inner circumferential face of a disc center hole, the gripping members being moveable radially between a retracted position and an engaged position, wherein respective lengths of the disc contacting faces are either a first length greater than a thickness of the inner circumferential face of the center hole or a second length equal to or smaller than the inner circumferential face of the center hole, and wherein more of the gripping members are of the first length than of the second length.

The present disclosure relates to the subject matter contained in Japanese patent application No. 2006-136170 filed on May 16, 2006, which is expressly incorporated herein by reference in its entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.

FIG. 1 is a schematic view showing a configuration of a CD publisher according to an exemplary embodiment of the present invention.

FIG. 2 is a perspective view showing a detailed example of an external appearance of a CD publisher.

FIG. 3 is a perspective view of the CD publisher in a status that doors are opened.

FIG. 4 is a perspective view showing an internal configuration of a CD publisher.

FIG. 5 is a perspective view showing a disc transport unit of a CD publisher.

FIG. 6 is an exploded perspective view of a transport arm of a disc transport unit.

FIG. 7 is a side view showing a gripping mechanism of a disc transport unit.

FIG. 8 is a plan view of the gripping mechanism.

FIGS. 9A and 9B are a sectional view and a plan view of gripping claws of the gripping mechanism.

FIGS. 10A and 10B are a perspective view and an exploded perspective view showing a connection mechanism of a transport arm and a timing belt.

FIG. 11 is a schematic flowchart showing a disc gripping operation of a disc transport unit.

FIG. 12 is a perspective view showing a printer of a CD publisher.

FIG. 13 is a plan view showing a printer tray of a printer.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, an example of a disc processing device including a disc gripping device according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

(Whole Configuration)

FIG. 1 is a schematic view showing a configuration of a CD publisher according to an exemplary embodiment of the present invention. The CD publisher 1 in this example includes a disc storage 3 for storing a disc 2 (blank disc 2A and a recorded disc 2B) such as a CD or a DVD, a disc drive 4 which records data into the disc 2 and retrieves data from the disc 2, a label printer 5 for printing a label including a title indicating recorded data, year/month/date of recording, and the like on a label side 2 a of the disc 2 in which data is recorded, a disc transport unit 6 for transporting the disc 2, and a control unit 7 responsible for controlling other units. The control unit 7 is connected to a higher rank device 8 such as a control server or a personal computer through a communication line including a LAN. From the higher rank device 8, a disc manufacturing request (data recording request or data rewriting request), a disc publishing request, or the like is input to the control unit 7.

The disc 2 is loaded or unloaded by the disc transport unit 6 with a disc tray 71 of the disc drive 4 drawn out to a disc replacing position 71A. The recording or retrieving of data is performed on the disc 2 which has been guided into the disc tray 71 in a processing position 71B where the disc tray 71 is inserted into the disc drive 4.

The label printer 5 is arranged below the disc drive 4 and includes a printer tray 81 for transporting the disc 2. The printer tray 81 reciprocates between a print position 81B and a disc replacing position 81A. The disc 2 is loaded or unloaded by the disc transport unit 6 in the disc replacing position 81A. In this example, the disc replacing position 81A of the printer tray 81 is right below the disc replacing position 71A of the disc tray 71 of the disc drive 4.

The disc storage 3 includes first and second stackers 11 and 12 which store the discs 2 stacked in the thickness direction. In this example, the first stacker 11 and the second stacker 12 are vertically arranged on the same shaft. Generally, the first stacker 11 serves as a blank disc stacker for storing a blank disc 2A, and the second stacker 12 serves as a recorded disc stacker for storing a recorded disc 2B.

A typical operation of the CD publisher 1 for recording a disc is described as follows. When a data recording request is received from the higher rank device 8, the CD publisher 1 takes out a blank disc 2A from the first stacker 11 of the disc storage 3, sets the blank disc 2A in the disc drive 4, and records record data which is supplied together with the data recording request. Next, the CD publisher 1 transports the recorded disc 2 to the label printer 5 and prints label printing data which is supplied together with the data recording request on a label side 2 a of the disc 2. The CD publisher 1 stores the recorded disc 2B after the printing process in the second stacker 12 of the disc storage 3. When there is a disc publishing request, the corresponding recorded disc 2B is taken out from the second stacker 12 by the disc transport unit 6 and discharged to a disc discharge port 13 (FIG. 2). As a result, the recorded disc 2B can be taken out from the CD publisher 1.

(Detailed Configuration Example of CD Publisher)

Next, a detailed configuration example of a CD publisher 1 according to an exemplary embodiment of the invention will be described with reference to FIGS. 2 to 11.

FIG. 2 is a perspective view showing an external appearance of the CD publisher 1. The CD publisher 1 includes a case 31 with doors 32 and 33 which can be opened or closed to the left or right sides attached to a front face of the case 3. An operation face 34 on which a display lamp, an operation button, and the like are arranged is formed below the doors 32 and 33, and a disc discharge port 13 is open beside the operation face 34.

FIG. 3 is a perspective view of the CD publisher 1 when the doors 32 and 33 are opened. The door 32 on the right side is locked closed, and a personal authorization mechanism, for example, a fingerprint sensor or the like is arranged on the operation face 34, so that the door 32 is configured to be opened by only an authorized person. Alternatively, the door 32 may be configured to be openable and closable according to a direction from the higher rank device 8. On the other hand, the door 33 on the left side is opened or closed at a time when an ink cartridge of the label printer 5 is to be replaced. When the door 33 is opened, a cartridge installation unit 36 is exposed. In the example, the cartridge installation unit 36 includes two upper and lower levels.

FIG. 4 is a perspective view of the CD publisher 1 when the doors 32 and 33 and a part of the case 31 are removed. Referring to FIGS. 3 and 4, inside the case 31 of the CD publisher 1, a blank disc stacker 11 and a recorded disc stacker 12 are vertically disposed on the same shaft in a left side part. The blank disc stacker 11 includes a slide plate 41 which can be extracted horizontally in a forward direction and a pair of left and right casing boards 42 and 43 in the shape of circular arcs which are disposed vertically on the slide plate 41. A stacker which can receive a disc 2A from an upper side and store the disc 2A stacked in a thickness direction is formed by the slide pate 41 and the casing boards 42 and 43. The operation of storing or supplementing the disc 2A in or to the blank disc stacker 11 can be simply performed by opening the door 32 and extracting the slide plate 41 in a forward direction.

The recorded disc stacker 12 in the lower side has the same configuration. The recorded disc stacker 12 includes a slide plate 44 which can be extracted horizontally in a forward direction and a pair of left and right casing boards 45 and 46 in the shape of circular arcs which are disposed vertically on the slide plate 44. A stacker which can receive a disc 2B from an upper side and store the disc 2B stacked on the same shaft is formed by the slide pate 41 and the casing boards 42 and 43.

A disc transport unit 6 is disposed in the rear side of the blank disc stacker 11 and the recorded disc stacker 12. The disc transport unit 6 includes a chassis 51 vertically attached to the case 31, a vertical guide shaft 54 vertically extending between horizontal support plate parts 52 and 53 which are disposed in upper and lower parts of the chassis 51, and a transport arm 55 attached to the vertical guide shaft 54. The transport arm 55 can lift along the vertical guide shaft 54 and rotate on the vertical guide shaft 54 to a left or right side.

In a rear part of a side of the disc transport unit 6, the disc drive 4 is disposed in an upper side, and the label printer 5 is disposed in a lower side. In FIGS. 3 and 4, a disc tray 71 of the disc drive 4 in the upper side is in a disc replacing position 71A in which the disc tray 71 is drawn out forward and the printer tray 81 of the label printer 5 in the lower side is in the disc replacing position 81A in the front side. The label printer 5 is preferably an ink jet printer, and ink cartridges 82 for each color are used as an ink supplying source. The ink cartridges 82 are installed to the cartridge installation unit 36 from a front side.

Here, between the each pair of left and right casing boards 42 and 43 and 45 and 46 of the blank disc stacker 11 and the recorded disc stacker 12, a gap is formed in which the transport arm 55 of the disc transport unit 6 can be lifted. In addition, a gap is formed between the stackers 11 and 12 respectively disposed in the upper and lower sides, so that the transport arm 55 can rotate horizontally and locate right above the stackers 11 and 12. When the disc tray 71 in the upper side is pushed to be inserted into the disc drive 4, the transport arm 55 of the disc transport unit 6 is lowered, so that the printer tray 81 in the disc replacing position can be accessed by the transport arm 55. Accordingly, the disc 2 can be transported to each part by performing combined operations of lifting and rotating to the left or right side of the transport arm 55.

(Disc Transport Unit)

FIG. 5 is a perspective view showing the disc transport unit 6. As described above, the disc transport unit 6 includes a chassis 51 vertically attached to the case 31, and a vertical guide shaft 54 is attached between the horizontal support plate parts 52 and 53 respectively disposed in the upper and lower parts of the chassis 51. The transport arm 55 is supported by the vertical guide shaft 54 so as to be liftable and rotatable.

A lifting mechanism of the transport arm 55 includes a motor 56 for lift which is a driving source. The rotation of the motor 56 is configured to be transferred to a driving side pulley 61 through a speed-reducing gear array including a pinion 57 which is attached to an output shaft of the motor, a mixed transfer gear 58, and a transfer gear 59. The driving side pulley 61 is supported in a position around an upper part of the chassis 51 so as to be rotatable on a horizontal rotating shaft (not shown). In a position around a lower part of the chassis 51, a driven side pulley 63 is supported so as to be rotatable on a horizontal rotating shaft 62 like the driving side pulley 61, and a timing belt 64 extends between the driving side pulley 61 and the driven side pulley 63. A rear end of the transport arm 55 is connected to one side of left and right belt parts of the timing belt 64 (The structure of the connection part will be described later with reference to FIG. 10 and other figures). As a result, when the motor 56 is driven, the timing belt 64 moves up and down, and thus the transport arm 55 attached thereto is lifted along the vertical guide shaft 54.

A rotating mechanism of the transport arm 55 includes a motor 65 for rotation which is a driving source, and a pinion (not shown) is attached to an output shaft of the motor 65. The rotation of the pinion is configured to be transferred to a final-stage gear 69 in the shape of a fan through a speed-reducing gear array having two mixed transfer gears 66 and 67. The final-stage gear 69 in the shape of a fan can rotate to the left or right side around the vertical guide shaft 54. In addition, a chassis 51 to which components of the lifting mechanism of the transport arm 55 are attached is mounted on the final-stage gear 69. When the motor 65 is driven, the final-stage gear 69 in the shape of a fan rotates to the left/right side, and accordingly, the chassis 51 which is mounted thereon rotates to the left/right side around the vertical guide shaft 54 as one structure. As a result, the transport arm 55 which is held by the lifting mechanism mounted on the chassis 51 rotates to the left/right side on the vertical guide shaft 54.

(Transport Arm and Gripping Mechanism)

FIG. 6 is an exploded perspective view showing major parts of the transport arm 55, FIG. 7 is a side view showing an internal structure of the transport arm 55, and FIG. 8 is a plan view showing the internal structure of the transport arm 55.

The transport arm 55 includes a thin and long arm base 55 a of which a front end part is in the shape of a half circle and an arm case 55 b in the shape of the same contour, which covers the arm base 55 a. A gripping mechanism 100 for gripping a disc 2 is installed in the arm base 55 a, and the gripping mechanism 100 is covered with the arm case 55 b not to be seen. Both the arm base 55 a and the arm case 55 b are preferably formed by a resin formation process.

The gripping mechanism 100 includes three gripping claws 101 to 103 in shapes of cylinders which are disposed in the same circle at equal angular intervals therebetween. The gripping claws 101 to 103 are vertically extruded downward through a circular hole 55 c formed in a front end of the arm base 55 a. The disc 2 can be gripped by inserting the three gripping claws 101 to 103 into the center hole 2 c of the disc 2 and pushing the gripping claws 101 to 103 outward in a radial direction.

The gripping claws 101 to 103 are formed under support pins 111 to 113 having diameters larger than those of the gripping claws 101 to 103. The support pins 111 to 113 extend upward through the circular hole 55 c of the arm base 55 a. The support pins 111 to 113 are respectively disposed in three rotation plates 121 to 123 which are disposed on a top face of the arm base 55 a. Rotation center shafts 131 to 133 are vertically installed in the arm base 55 a at equal angular intervals therebetween in a same circle in a status that the rotation center shafts surround the circular hole 55 c. The rotation plates 121 to 123 are supported so as to be rotatable on the rotation center shafts 131 to 133, respectively. Pins 101 a to 103 a in the shapes cylinders to be described later are preferably formed of resin such as POM in the same bodies as the rotation plates 121 to 123, respectively.

The rotation plates 121 to 123 include front and rear arm parts 121 a, 121 b, 122 a, 122 b, 123 a, and 123 b, respectively, which extend along the arm base 55 a in an approximate circumference direction of the circular hole 55 c and support arms 121 c to 123 c which are extruded from the center of the rotation toward an inner side of the circular hole 55 c. On rear sides of front ends of the support arms 121 c to 123 c, the support pins 111 to 113 are vertically fixed, respectively.

A rear end of the rear arm part 122 b of the rotation plate 122 is in contact with a front end face of the front arm part 121 a of the rotation plate 121 so as to be slidable. Likewise, a rear end of the rear arm part 123 b of the rotation plate 123 is in contact with a front end face of the front arm part 122 a of the rotation plate 122 so as to be slidable. A rear end of the rear arm part 121 b of the rotation plate 121 is in contact with a front end face of the front arm part 123 a of the rotation plate 123 so as to be slidable. Here, the rotation plates 121 to 123 are configured to rotate in the same direction by properly setting inclination angles of the front end faces of the front arm parts 121 a to 123 a.

A helical extension spring 124 extends between the front arm part 121 a of the rotation plate 121 and the front arm part 122 a of the rotation plate 122. By the tensile force of the helical extension spring 124, the rotation plates 121 to 123 are maintained in a contacting status without rattling, and a biasing force is applied to the rotation plate 121 in a direction (direction in which the gripping claws 101 to 103 are widened) denoted by an arrow R1 shown in FIG. 8.

In this status, a circumscribed circle of the gripping claws 101 to 103 which are respectively attached to the front ends of the support arms 121 c to 123 c of the rotation plates 121 to 123 has a diameter larger than an inner diameter of the center hole 2 c of the disc 2. In this state, when one rotation plate, for example, the rotation plate 121, is rotated in a direction denoted by an arrow R2, the other two rotation plates 122 and 123 rotate by the same angle in the same direction in concert with the rotation of the rotation plate 121. As a result, the support arms 121 c to 123 c of the rotation plates 121 to 123 move toward the center of the circular hole 55 c, and the gripping claws 101 to 103 attached to the front ends thereof can be collected so as to be inserted into the center hole 2 c of the disc 2. In this status, when the gripping claws 101 to 103 are inserted into the center hole 2 c of the disc 2, and the rotation plates 121 to 123 are rotated in a reverse direction R1, the gripping claws 101 to 103 can be pushed outward in a radial direction. As a result, the gripping claws are pushed to the inner circumference 2 d of the center hole 2 c of the disc, so that the disc 2 is gripped.

In the gripping mechanism 100 of this example, the following mechanisms are included for rotating the rotation plates 121 to 123. An operation arm 121 d which extends to the opposite side of the support arm 121 c is formed in the rotation plate 121. A front end of an arm part 125 a in one side of an L-shaped link 125 is connected to a front end of the operation arm 121 d with the front end of the arm part 125 a being freely rotated. The L-shaped link 125 can be rotated around a bent part, and a front end of the arm part 125 b in the opposite side is connected to an operation rod 126 a of an electromagnetic solenoid 126. When the electromagnetic solenoid 126 is in an “off” status, the operation rod 126 a is extended as shown in FIG. 8. When the electronic solenoid 126 is shifted to an “on” state, the operation rod 126 a is pulled in against the spring force of a built-in spring to rotate the L-shaped link 125. The rotation of the L-shaped link 125 is transferred to the rotation plate 121, the rotation plate 121 is rotated in a direction R2, and the other two rotation plates 122 and 123 are rotated by the same angle in the same direction in synchronization with the rotation of the rotation plate. As a result, separation of the gripping claws 101 to 103 can be shrunken.

As described above, in the gripping device 100 of this example, three gripping claws 101 to 103 are moved in a radial direction to be in a disc open position (retracted position) in which the gripping claws can be inserted into the center hole 2 c of the disc 2 and a disc gripping position (engaged position) in which the gripping claws are pushed to the inner circumferential face 2 d of the center hole 2 c of the disc. By acquiring the amounts of strokes of the gripping claws 101 to 103 sufficiently, the gripping claws 101 to 103 can be inserted into the center hole 2 c of the disc without touching a surface of the disc. Accordingly, it is not required to form long inclination faces vertically in the front ends of the gripping claws 101 to 103 for guiding the disc 2, and the lengths of the gripping claws 101 to 103 can be shortened to be substantially equal to the thickness of the disc 2.

In addition, the rotation plates 121 to 123 disposed in a planar direction can be held to contact with one another, and when one rotation plate 121 is rotated, the other two rotation plates 122 and 123 are configured to rotate by the same angle in the same direction in concert with the rotation of the rotation plate 121. Accordingly, the rotation mechanism of the rotation plates 121 to 123 can be flattened. In other words, the mechanism for moving the gripping claws 101 to 103 can be formed in a flat configuration.

As described above, in this example, since the gripping claws 101 to 103 can be shortened, and the mechanism for moving the gripping claws 101 to 103 can be formed in a flat configuration, the gripping device can be made thin. In addition, since the gripping plates 122 and 123 have the same shape, these components can be commonly used. Accordingly, there is an advantage that the manufacturing cost can be reduced.

(Gripping Claw)

Next, the gripping claws 101 to 103 in this example will be described with reference to FIG. 9. FIG. 9( a) is a sectional view of the gripping claws 101 and 103, and FIG. 9( b) is a plan view of the gripping claws 101 to 103. The gripping claws 101 to 103 include pins 101 a to 103 a in the shape of a cylinder which extrude downward from lower end faces 111 a to 113 a of support pins 111 to 113 and elastic cylinders 101 b to 103 b formed of rubber or the like which surround the pins 101 a to 103 a concentrically. Under the lower ends of the pins 101 a to 103 a, heads 101 c to 103 c having large diameters for preventing falling-out are formed.

The circular outer circumferential faces 101 d to 103 d of the elastic cylinders 101 b to 103 b of the gripping claws 101 to 103 are disc contacting faces which can be contacted to the inner circumferential face 2 d of the center hole 2 c of the disc 2. The lengths of the shafts of the gripping claws 101 (first gripping claw) and 102 (second gripping claw) are configured to be greater than the length of the shaft of the gripping claw 103 (third gripping claw) and to be at least greater than the thickness of the inner circumferential face 2 d of the disc 2 to be gripped. In this example, the lengths of the elastic cylinders 101 b and 102 b of the gripping claws 101 and 102, as shown in FIG. 9( a), are configured to be a length extending the whole inner circumferential face 2 d of the stacked upper disc 2(1) and at least an upper part of the inner circumferential face 2 d of a lower disc 2(2). To the contrary, the length of the elastic cylinder 103 b of the gripping claw 103 is configured to be equal to or less than the thickness of the inner circumferential face 2 d of the disc 2 to be gripped and, in this example, configured to be slightly less than the thickness of the inner circumferential face 2 d.

As shown in FIG. 9, the gripping claws 101 to 103 are inserted into a center hole 2 c of an uppermost disc 2(1) among discs stacked up in a thickness direction and pushed outward in a radial direction. In other words, disc contacting faces formed with elastic members 101 b and 102 b of the long gripping claws 101 and 102 are elastically transformed by being pushed to the inner circumferential face 2 d of the disc center hole 2 c. However, parts 101 e and 102 e (only a part 101 e is shown in the figure) protruded in the disc contacting face from the disc center hole 2 c to the opposite side are not elastically transformed and are penetrated into the rear side of the disc 2(1). In other words, the parts 101 e and 102 e penetrate into a gap between the rear side of the upper disc 2(1) to be gripped and a front side of a lower disc 2(2). In addition, lower ends 101 f and 102 f (only a lower end 101 f is shown in the figure) of the elastic cylinders 101 b and 102 b are pushed to an upper part of the inner circumferential face 2 d of the center hole 2 c of the lower disc 2(2). On the other hand, a disc contacting face of the short gripping claw 103 is pushed to only the inner circumferential face 2 d of the center hole of the uppermost disc 2(1).

The upper disc 2(1) is gripped by three gripping claws 101 to 103 assuredly. In addition, the upper disc 2(1) is assuredly gripped by the elastic transformation of disc contacting faces of two gripping claws 101 and 102, so that the upper disc 2(1) does not also fall off the gripping claws 101 and 102 in the disc thickness direction. Only parts of the disc contacting faces of two long gripping claws 101 and 102 contacts the lower disc 2(2), and the width of outer sides of the lower parts 101 f and 102 f is about 87% of an inner diameter of the center hole 2 c. Accordingly, when the gripping claws 101 to 103 are lifted, only the upper disc 2(1) is lifted.

When the gripping claws 101 to 103 are pushed in the radial direction, the position of the upper disc 2(1) in the disc planar direction is fixed by the three gripping claws, but since the lower disc 2(2) contacts only two gripping claws 101 and 102, the lower disc 2(2) is pushed in the disc planar direction by the gripping claws 101 and 102. Accordingly, the lower disc 2(2) slides in a slightly horizontal direction relatively with respect to the upper disc 2(1). Although when the upper and lower discs 2(1) and 2(2) are tightly contacted, the lower disc 2(2) slides to penetrate the air between the upper and lower discs 2(1) and 2(2), and accordingly, the tight contact is alleviated or released. Accordingly, only the upper disc 2(1) can be lifted assuredly.

In addition, there is an advantage that the disc 2 is not damaged when the disc 2 is gripped since disc contacting faces of the three gripping claws 101 to 103 are formed of the elastic cylinders 101 b to 103 b.

Generally, the number of gripping claws is three, but the number of the gripping claws may be four or more. When the number of the gripping claws is four or more, the numbers and disposition of long gripping claws and short gripping claws are properly set, for example, by disposing the long gripping claws in an area less than a ½ times the inner circumferential face which does not include a diameter of the center hole or the like. That is, the long gripping claws are disposed such that the distance between the long gripping claws is smaller than the diameter of the center hole.

(Disc Detecting Mechanism)

The gripping device 100 includes a disc detecting mechanism for controlling a stop position (insertion amount) at a time when the gripping claws 101 to 103 are inserted into the center hole 2 c of the disc 2. Referring to FIGS. 6 to 9, the disc detecting mechanism 140 in this example is equipped with a disc detecting lever 141 and a disc detector 142 including a photo coupler. The disc detecting lever 141 is an L-shaped lever including a main part 141 a in the shape of a straight line and a front end part 141 b which bends at a right angle downward from a front end of the main part 141. A rear end of the main part 141 a is attached to a top face of the arm base 55 a where the rear end of the main part 141 a can be rotated freely in an upper/lower direction. The main part 141 a of the disc detecting lever 141 is disposed on the top face of the arm base 55 a, and the front end 141 b of the main part 141 a protrudes downward from a rear side of an opening part 55 d through the opening part which is formed on the arm base 55 a. In a side of the main part 141 a, a detection plate 141 c which is protruded horizontally is formed. The detection area 142 a of the disc detector 142 is disposed in the moving trajectory of the detection plate 141 c which is accompanied by the upward/downward movement of the disc detecting lever 141.

When the disc 2 is not gripped, the disc detecting lever 141 is maintained horizontally on the arm base 55 a. In this instance, the detection plate 141 c is positioned within a detection area 142 a of the disc detector 142 and is in an “off” status in which detection light passing the detection area 142 a is blocked. As the gripping claws 101 to 103 are inserted into the center hole 2 c of the disc 2 by lowering the transport arm 55, a front end part 141 b of the disc detecting lever 141 contacts the surface of the disc 2, and the disc detecting lever 141 is lifted in accompaniment with the insertion of the gripping claws 101 to 103.

As shown in FIGS. 7 and 9( a), right before the lower end faces 111 a to 113 a of the support pins 111 to 113 supporting the gripping claws 101 to 103 contact the surface of the disc 2 after the gripping claws 101 to 103 have been completely inserted into the center hole 2 c of the disc 2, the detection plate 141 c gets off the detection area 142, and the disc detector 142 is shifted to an “on” position. Accordingly, the insertion of the gripping claws 101 to 103 into the center hole 2 c of the disc 2 is detected.

(Connection Mechanism of Transport Arm and Timing Belt)

When the insertion position of the gripping claws 101 to 103 is controlled by using the detection mechanism 140, as shown FIGS. 7 and 9( a), there is a case where the inserting operation of the gripping claws 101 to 103 cannot be stopped precisely at a time when the gripping claws 101 to 103 are completely inserted into the center hole 2 c of the disc 2 due to a manufacture error of the disc detecting lever 141, an attachment error of the disc detecting lever 141, an attachment error of the disc detector 142, a detection error of the disc detector 142, and the like. When the insertion is not sufficient, the disc 2 cannot be gripped by the gripping claws 101 to 103, and accordingly there is a possibility that a gripping defect occurs. On the other hand, when the gripping claws 101 to 103 are excessively inserted, the lower end faces 111 a to 113 a of the support pins 111 to 113 to which the gripping claws 101 to 103 are attached and the like come to contact the surface of the disc 2 to damage the disc 2, and there is a possibility that the disc may be destroyed in some cases. In order to prevent this disadvantage, in this example, a connection mechanism having a configuration that the transport arm 55 is connected to a timing belt 64 which is a lifting mechanism through an elastic member is used.

FIG. 10( a) is a partial perspective view showing a connection mechanism part, and FIG. 10( b) is an exploded perspective view of the connection mechanism part. Referring to FIGS. 7 and 10, the transport arm 55 is connected to a belt clip 152 which is fixed to a timing belt 64 through a spring member 151. A top face 153 facing downward and a ground shaft 154 in the shape of a cylinder which extends vertically from the top face 153 downward are formed in the rear end of the arm base 55 a of the transport arm 55. The belt clip 152 includes an upper end face 152 a which can contact to the top face 153 of the arm base side from a lower side, a shaft hole 152 b which extends from the upper end face 152 a through the belt clip 152, and a fixing part 152 c which is fixedly connected to the timing belt 64.

The belt clip 152 is attached to a rear end of the arm base 55 a where the ground shaft 154 passes through the shaft hole 152 b of the belt clip 152, and the upper end face 152 a of the belt clip 152 contacts the top face 153 from the lower side. Accordingly, the transport arm 55 can be moved upward with respect to the belt clip fixed to the timing belt 64 through support parts including the ground shaft 154, the shaft hole 152 b, the top face 153, and the upper end face 152 a. In other words, the transport arm 55 can move in a direction that the gripping claws 101 to 103 are pulled up from the center hole 2 c of the disc 2.

A groove 152 d which receives the spring member 151 from the lower side is formed in a part disposed in a front side from the shaft hole 152 b on a lower face of the belt clip 152. The spring member 151 is attached to a spring hanger 155 which is formed in a rear end of the arm base 55 a and always biases the belt clip 152 upward. Accordingly, the arm base 55 a is pushed to the belt clip 152 by the spring member 151, thus the movement of the arm base 55 a upward is blocked.

When the timing belt 64 is driven (see FIG. 5) by a lifting motor 56, the belt clip 152 fixed to the timing belt 64 lifts in one body. When an excessive load is not applied, the arm base 55 a lifts along the vertical guide shaft 54 in one body with the belt clip 152 which is fixed to the timing belt 64 by the spring force of the spring member 151.

Here, when the transport arm 55 is lowered and the gripping claws 101 to 103 disposed in the front ends of the gripping claws 101 to 103 are inserted into the center hole 2 c of the disc 2, it is assumed that the lower end faces 111 a to 113 a of the support pins 111 to 113 supporting the gripping claws 101 to 103 collide with the surface of the disc 2 before the disc 2 is detected by the above-described disc detecting mechanism 140.

In this case, an excessive load applies temporarily to the transport arm 55, and the spring member 151 is elastically transformed to be pushed in up/down directions. Thus, the collision force is alleviated owing to the elastic transformation of the spring member 151. Thereafter, when the belt clip 152 is lowered, the transport arm 55 maintains its position without being lowered since the spring member 151 is elastically transformed. As a result, the disadvantage in that the disc 2 is excessively pushed and destroyed or the like can be prevented.

The amount of insertion of the gripping claws 101 to 103 into the center hole of the disc is configured to be slightly sufficient, for example, with consideration of a detection error (deviation of stop positions of the gripping claws 101 to 103) of the disc detecting mechanism 140 caused by a manufacture error, manufacture errors of the components, attachment errors thereof, and the like. Accordingly, the disc gripping defect of the gripping claws 101 to 103 can be prevented. In addition, when the support pins 111 to 113 (gripping members) to which the gripping claws 101 to 103 are attached contact the surface 2 b of the disc in inserting the gripping claws 101 to 103, the spring member 151 which is an elastic member is elastically transformed, and accordingly, the collision force applied to the disc 2 is alleviated. In addition, after the support pins 111 to 113 contact the disc 2, the spring member 151 is elastically transformed to push in the up/down directions, and accordingly, the transport arm 55 does not move further in the insertion direction. As a result, the disc 2 is not damaged by the support pins 111 to 113.

In addition, in this example, the transport arm 55 supporting the gripping claws 101 to 103 is connected to be able to move with respect to the timing belt 64 which is a lifting mechanism and is always blocked from moving by the spring member 151. Alternatively, for example, when the rotation plates 121 to 123 in which the support pins 111 to 113 of the gripping claws 101 to 103 are formed are attached to be able to move in up/down directions with respect to the rotation center shafts 131 to 133, and the movement of the rotation plates 121 to 123 are to be blocked from an upper side by an elastic member such as a helical compressive spring, the elastic member is elastically transformed in up/down directions after the support pins 111 to 113 contact the disc 2 although the transport arm 55 moves in the insertion direction, and accordingly, the support pins 111 to 113 do not move further in the insertion direction. As another exemplary embodiment, the support pins 111 to 113 are configured to be components separated from the rotation plates 121 to 123, and the support pins 111 to 113 may be attached to the rotation plates 121 to 123 though a spring member.

(Operation of Disc Gripping)

FIG. 11 is a schematic flowchart showing a disc gripping operation performed by the disc transport unit 6 having the above-described structure.

For example, a case where a blank disc 2A stored in a blank disc stacker 11 is gripped and lifted to be transported to another part will be described. In this case, the position of the transport arm 55 is determined to be a predetermined position right above the blank disc stacker 11 under the control of the control unit 7.

The electronic solenoid 126 of the gripping mechanism 100 which is installed in the transport arm 55 is turned on (step ST1). When the electronic solenoid is shifted to “on”, its operation rod 126 a is pulled in, the movement of the operation rod 126 a is transferred to the rotation plate 121 through the L-shaped link 125, and accordingly, the rotation plate 121 is rotated by a predetermined angle in a direction of arrow R2 shown in FIG. 8. Remaining rotation plates 122 and 123 are rotated by the same angle in the same direction, the gripping claws 101 to 103 which are attached to front ends of the support arms 121 c to 123 c of the three rotation plates 121 to 123 respectively move in directions approaching one another, and accordingly, the gripping claws are collected to be inserted into the center hole 2 c of the disc 2A.

Thereafter, the motor 56 for lifting the transport arm is driven to start a lowering operation of the transport arm 55 (step ST2). When the transport arm 55 is lowered to approach an uppermost blank disc 2A, the detection lever 141 of the disc detecting mechanism 140 which is built in the transport arm 55 contacts a surface of the blank disk 2A. Then, the detection lever 141 moves relatively upward in accompaniment with the lowering of the transport arm 55, the detection plate 141 c of the detection lever 141 gets off the detection area 142 a of the disc detector 142, and accordingly, the disc detector 142 is shifted to “on” (step ST3). The transport arm 55 is lowered by a predetermined distance to stop the transport arm 55, and the gripping claws 101 to 103 of the gripping device 100 disposed in the transport arm 55 are inserted into the center hole 2 c of the blank disc 2A (step ST4). When a stepping motor is used as the motor 56 for lifting the transport arm, for example, the position of the transport arm 55 is determined by the number of steps of the stepping motor.

After the above-described insertion process in which the three gripping claws 101 to 103 are inserted into the center hole 2 c of the blank disc 2A to be gripped is completed, the gripping claws 101 to 103 inserted into the center hole 2 c are pushed outward in a direction of the diameter of the center hole 2 c to be pushed to the inner circumferential face 2 d of the center hole 2 c. In other words, the electronic solenoid 126 is turned off, so that the operation rod 126 a is returned to the protrusion position (step ST5). As a result, the rotation plate 121 connected to the operation rod 126 a through the L-shaped link 125 is rotated in the direction of arrow R1 shown in FIG. 8 by the spring force of the helical extension spring 124 to return to its original position. In the linkage of the movement of the rotation plate 121, the remaining two rotation plates 122 and 123 are rotated by the same angle in the same direction to return to their original positions. Therefore, a disc gripping status in which the gripping claws 101 to 103 attached to the rotation plates 121 to 123 are pushed outward in the direction of the diameter of the center hole and into the inner circumferential face 2 d of the center hole of the blank disc 2A.

After the above-described disc gripping process is completed, a disc lifting process in which the gripped blank disc 2A is lifted by lifting the transport arm 55 via the gripping claws 101 to 103 is performed (steps ST11 to ST15).

In the disc lifting process of this example, until the transport arm 55 is lifted by a predetermined distance, that is, until the gripping claws 101 to 103 move by a predetermined distance in a direction opposite to the insertion direction, the transport arm 55 is lifted intermittently. In other words, a lifting operation which lifts the transport arm 55 by a predetermined distance at a predetermined speed, and a stop operation which stops the transport arm 55 for a predetermined time are repeated a predetermined number of times (steps ST11 to ST13). When the motor 56 for lifting the transport arm is a stepping motor, the lifting distance can be managed by the number of steps of the stepping motor.

After the intermittent moving process is performed, it is detected whether the blank disc 2A is gripped and lifted by the gripping claws 101 to 103 based on an output of the disc detecting mechanism 140 (step ST14). When the blank disc 2A is lifted, the detection lever 141 of the disc detecting mechanism 140 is in a status that the detection lever 141 is moved upward by the lifted blank disc 2A, and the disc detector 142 is in an “on” status. Accordingly, it can be detected whether the blank disc 2A is assuredly gripped and lifted by the gripping claws 101 to 103 based on the output of the disc detecting mechanism 140.

When the blank disc 2A is not lifted, the process is returned to the step ST1 again, and the gripping and lifting operation of the blank disc 2A is performed again from the start. When the blank disc 2A is lifted, a high-speed continuous moving process in which the transport arm 55 is lifted continuously to a position of a predetermined height at a speed higher than the lifting speed of the transport arm in the intermittent moving process is performed (step ST15).

In this example, the transport arm 55 is, at first, lifted intermittently at a low speed. As described above, the transport arm 55 is connected through the spring member 151 to the timing belt 64 which is a driving member of the lifting mechanism. When there are deviations in the insertion stop positions of the gripping claws 101 to 103, which are determined by the operation of the disc detecting mechanism 140, the gripping claws 101 to 103 are inserted into the center hole 2 c of the disc without incurring any damage to the disc 2A owing to the elastic transformation of the spring member 151, and the lower end faces 111 a to 113 a of the support pins 111 to 113 to which the gripping claws 101 to 103 are attached contact the surface of the disc.

The transport arm 55 is pushed to the front side of the disc by the spring force of the spring member 151. In other words, the blank disk 2A is pushed to the blank disc 2A in the lower side by the spring force of the spring member 151 from the upper side. When the gripping claws 101 to 103 are pushed in this manner, if the friction force between the upper and lower blank discs 2A is higher than the pushing force of the gripping claws 101 to 103, the blank disc 2A cannot be moved in a horizontal direction. As a result, it is possible that the inner circumferential face 2 d of the center hole 2 c of the blank disc cannot be gripped assuredly from the inside by the three gripping claws 101 to 103.

Particularly in this example, as shown in FIG. 9, it is possible that the gripping claws 101 and 102 cannot be opened by pushing the discs in a horizontal direction when long gripping claws 101 and 102 extend to the inner circumferential faces of the two discs and the discs are pushed from the up side.

In order to prevent this disadvantage, when the transport arm 55 is lifted in the gripping operation of this example, at first, an intermittent lifting operation is repeated. The pushing force of the blank disc 2A is slowly alleviated by repeating slight lifting and stopping operations of the transport arm 55. When the pushing force applied to the blank disc 2A is alleviated to some degree or the pushing force disappears, it becomes possible to push out the blank disc 2A in a horizontal direction by the gripping claws 101 to 103. As a result, as described with reference to FIG. 9, the upper and lower blank discs 2A are relatively slid by the gripping claws 101 to 103, and accordingly, only the upper blank disc 2A is gripped. Since the blank disc 2A is assuredly gripped by this intermittent moving process, a disadvantage in that the blank disc 2A falls off or the like while the blank disc 2A is lifted can be prevented.

(Detailed Example of Label Printer)

FIGS. 12 and 13 are a perspective view showing a detailed example of a label printer 5 and a plan view showing a printer tray 81 of the label printer, respectively. Hereinafter, the configuration of the label printer 5 will be described with reference to the figures.

The label printer 5 includes a chassis 83 and a carriage guide shaft 84 extending horizontally between left and right side plate parts in a rear side of the chassis 83, so that a head carriage 85 in which an ink jet head (not shown) is built can reciprocate in left/right directions along the carriage guide shaft 84. A carriage driving mechanism includes a timing belt 86 that extends horizontally in left/right directions and a carriage motor 87 that is used for driving the timing belt 86.

The ink jet head which is built in the head carriage 85 has a nozzle face disposed downward, and a printer tray 81 can reciprocate rear side positions of the ink jet head horizontally in front/rear directions. The printer tray 81 has a right end that is supported by a guide shaft 88 extending horizontally in the front/rear directions and a left end that is supported by a guide rail 89 extending horizontally in the front/rear directions such that the guide rail 89 can slide. A driving mechanism of the printer tray 81 has a configuration including a timing belt 90 that extends horizontally in the front/rear directions and a tray motor 91 that is used for driving the timing belt 90.

The printer tray 81 includes a shallow depression part 81 a that is used for loading a disc 2 in a front face of a rectangular shaped plate. A center part of the depression part 81 a includes three vertical claws 92 to 94 disposed at 60-degree intervals in the same circle. One vertical claw 94 can be moved in a radial direction, and the remaining two vertical claws 92 and 93 are disposed in a fixed position. One vertical claw 94 is configured to be moved by a driving mechanism such as an electronic solenoid that is not shown in the figure.

When the disc 2 falls from an upper side into the depression part 81 a with a label side 2 a up, as shown in FIG. 13, three vertical claws 92 to 94 are inserted into a center hole 2 c of the disc 2. Thereafter, when the vertical claw 94 is moved slightly outward in a radial direction, the three vertical claws 92 to 94 are pushed to an inner circumferential face 2 d of the center hole 2 c of the disc 2 from an inner side. Accordingly, the disc 2 is maintained in the printer tray 81. The printer tray can be moved to a print region of the ink jet head by driving the tray motor 91 to move the printer tray 81 to a rear side along the guide shaft 88. Thereafter, printing on a print side of the disc 2 can be performed by the ink jet head.

The present invention is not limited to the above-described embodiments and various modifications thereof can be made. For example, a case where pins 101 a to 103 a in the shape of cylinders and elastic cylinders 101 b to 103 b made of rubber or the like which surrounds the pins 101 a to 103 a concentrically are used is described in the exemplary embodiments of the invention, but a mechanism in which pins directly grip the disc without the elastic cylinders 101 b to 103 b may be used since the mechanism can lift only an uppermost disc. However, when an elastic member such as silicon rubber is used, gripping can be improved in gripping or transporting a disc.

In addition, in the above-described embodiments, a case where all the gripping claws 101 to 103 are moved to a center side was proposed, but, as in Patent Document 2, only one gripping claw may be moved to the center side since the uppermost disc can be always gripped and lifted. 

1. A disc gripping device for gripping a disc by inserting at least three gripping members into a center hole of a disc and expanding at least one of the gripping members in a radial direction to engage an inner circumferential face of the center hole, wherein the at least three gripping members include: a first gripping member having a first disc contacting face for contacting the inner circumferential face of the center hole, a length of the first disc contacting face as measured in a direction perpendicular to the thickness of the disc being greater than a thickness of the inner circumferential face of the center hole; a second gripping member having a second disc contacting face for contacting the inner circumferential face of the center hole, a length of the second disc contacting face as measured in the direction perpendicular to the thickness of the disc being equal to or smaller than the thickness of the inner circumferential face of the center hole, and a third gripping member having a third disc contacting face for contacting the inner circumferential face of the center hole, wherein all of the at least three gripping members are movable in a radial direction, wherein each of the at least three gripping members has an elastic cylinder including a shaft member and an elastic member covering an outer circumferential face of the shaft member, and wherein the respective disc contacting faces comprise at least a part of the outer circumferential face of the elastic cylinder.
 2. The disc gripping device according to claim 1, wherein a length of the third disc contacting face as measured in the direction perpendicular to the thickness of the disc is greater than a thickness of the inner circumferential face of the center hole, and wherein a distance between the first gripping member and the third gripping member is smaller than a diameter of the center hole.
 3. The disc gripping device according to claim 1, wherein the gripping members are moveable between a retracted position and an engaged position, the gripping members being pushed toward the engaged position by a spring force.
 4. The disc gripping device according to claim 3, wherein the gripping members are coupled with one another such that displacement of the first gripping member serves to displace the second and third gripping members.
 5. The disc gripping device according to claim 4, further comprising an actuator coupled with the first gripping member, the actuator driving the gripping members from the engaged position to the retracted position against the spring force.
 6. A disc processing apparatus comprising: a disc storage that stores discs stacked in a thickness direction; a disc processor including at least one of a disc drive that performs data writing or data reading and a label printer that performs printing on a label face of the discs; and a disc transport unit for transporting the discs between the disc storage and the disc processor, wherein the disc transport unit includes the disc gripping device according to claim
 1. 